Why does Telemachus doubt that it is indeed his father, Odysseus, who he sees enter the swineherds hut?

Telemachus last saw his father twenty years ago when he (Telemachus) was a very young
child. He spent the first four books of the Odyssey searching for his father to no avail and
seems to have given up hope. He has not the least idea what Odysseus looks like, though he
assumes he will look like a king. Odysseus does look more regal after Athena touches him with
her wand and he returns to the hut, but Telemachus recognizes that this is the same stranger
with whom he has just been conversing and leaps to the conclusion that he is a god in disguise,
since only a god could alter his appearance so thoroughly.

It is only when
Odysseus says that the change in his appearance has indeed been brought about by divine power,
that of the goddess Athena, that Telemachus finally accepts that his father has
returned.

It is obvious that, despite their difference in rank, Telemachus
has come to look upon Eumaeus as a father figure, and there is a strange prefiguring of his
reunion with Odysseus when he...